Cold starting of fuel injected gasoline engines has always caused the designers of fuel injection systems much concern. The main reason for the concern is that during the cold starting sequence, the battery voltage is often low and therefor the power necessary to turn on the injectors may not be available. With this in mind, many sophisticated and complex driver circuits have been developed.
In order to solve this problem, many fuel injection systems have used an extra fuel injector placed upstream of the intake manifold to inject extra fuel for a predetermined period of time. Other solutions have been to add a correction length to each fuel injection pulse as it is calculated. This extends a normally longer pulse to an even greater length and may, under certain circumstances, cause pulse overlap. Still other solutions have included the addition of fuel pulses during the time that the engine is cold. See U.S. Pat. No. 4,096,831 issued on June 27, 1978 to R. Gunda and entitled "Frequency Modulated Fuel Injection System". Other solutions use a low impedance injector coil and special peak and hold current driver circuits. In those applications wherein the injectors are energized in sequence and not as a group, this requires one such special circuit for each injector position.
It is a principal advantage of the present invention to selectively control the voltage applied to the fuel injector driver circuit during low voltage conditions. It is a further advantage of the present invention to effectuate significant cost savings by a reduction in the number of components needed to control the operation of the fuel injectors and fuel injector driver circuits. It is still a further advantage of the this system to simplify the injector driver circuit to a basic switch circuit and remove the requirement of complex peak and hold current circuits. It is yet another advantage of this system to utilize high impedance injector coils thereby reducing the electrical power consumption of the overall fuel injection system.